1. Field of the Invention
This invention relates to a switch apparatus, and is particularly concerned with a switch apparatus for adjusting an automobile seat position.
2. Description of the Prior Art
Seesaw type switches are capable of conducting large currents, and are therefore often extensively used to for controlling the connection of a power source to an electric motor, such as an automobile seat positioning motor.
FIGS. 10 to 12(b) show a prior art seesaw switch. As shown in FIG. 10, the prior art seesaw switch includes a switch housing 1 which includes first and second parallel box sections 1b and 1c. Each box section 1b and 1c includes a bottom surface and an open top. Side plates 1a (only one shown) are formed on outer parallel walls of the box sections 1b and 1c. A lever 5 is pivotably mounted to the side plates 1a using a shaft 2.
As shown in FIG. 11, the lever 5 has a forked shape and includes a first protrusion 5c extending into the first box section 1b and a second protrusion 5d extending into the second box section 1c. A knob 3 is connected to an upper portion of the lever 5 to facilitate manual actuation of the seesaw switch. A pair of fitting holes 5a and 5b are formed in a lower surface of the protrusions 5c and 5d, respectively. Driving rods 7a, 7b are slidably housed in the fitting holes 5a and 5b , respectively, and are biased away from the lever 5 by springs 6a, 6b, respectively.
In addition, first and second fixed contacts 10a and 10b are fixedly connected to the bottom surface at opposite ends of the first box section 1b, and third and fourth fixed contacts 11a and 11b are connected to the bottom surface at opposite ends of the second box section 1c. A first pivot plate 12a is fixedly connected to the bottom surface of the first box section 1b at a position substantially midway between the fixed contacts 10a and 10b, and a second pivot plate 12b is fixedly connected to the bottom surface of the second box section 1c at a position substantially midway between the fixed contacts 11a and 11b. In addition, moving contact pieces 8a and 8b, which are formed by bending an elongated metallic plate, are pivotably supported on the pivot plates 12a and 12b, respectively.
As shown in FIG. 12(a), when the prior art seesaw switch is in a neutral (unactuated) position, the driving rods 7a and 7b bias the moving contact pieces 8a and 8bagainst the pivot plates 12a and 12b respectively. Note that the pivot plate 12a is positioned relative to the driving rod 7a such that, in the neutral position, the moving piece 8a pivots about the pivot plate 12a such that a first end of the moving contact piece 8a is held in contact with the fixed contact 10a, and a second end of the moving contact piece is separated from the fixed contact 10b. Likewise, the pivot plate 12b is positioned relative to the driving rod 7b such that, in the neutral position, the moving piece 8b pivots about the pivot plate 12b such that a first end of the moving contact piece 8b is held in contact with the fixed contact 11b, and a second end of the moving contact piece 8b is separated from the fixed contact 11a.
As shown in FIG. 12(b), when a first end 3a of the knob 3 is pressed downward, the lever 5 is pivoted counterclockwise, and the driving rod 7a slides in a first direction on the moving contact piece 8a toward the fixed contact 10a. When the driving rod 7a passes over the pivot plate 12a, the moving contact piece 8a pivots clockwise around the support plate 12a, thereby causing the second end of the moving contact piece 8a to contact the fixed contact 10b and lifting the first end of the movable contact piece 8a away from the fixed contact 10a. Note that, although the driving rod 7b slides on the second moving contact 8b in the first direction, the second moving contact 8b remains pivoted such that the first end contacts the fixed contact 11b because the driving rod 7b does not pass over the pivot plate 12b. In this position, a first switching operation is carried out. When released, the driving rod 7b biases the lever 5 back into the neutral position.
In a similar manner, when a second end 3b of the knob 3 is pressed downward from the neutral position, the lever 5 is pivoted clockwise, and the driving rods 7a and 7b slide on the moving contact pieces 8a and 8b toward the fixed contacts 10b and 11b. When this occurs, the first moving contact piece 8a remains in contact with the fixed contact 10a, and the second moving contact pivots about the pivot plate 12b to contact the fixed contact 11b, thus effecting a second switching operation.
FIGS. 13 to 15 illustrate a prior art switch apparatus for adjusting automobile seat positions which comprises multiple seesaw switches, as described above. The switch apparatus includes a housing 17 in which are located a seesaw switch A for adjusting longitudinal seat positions, a seesaw switch B for adjusting seat front heights and a seesaw switch C for adjusting seat rear heights. A slide plate 19 is slidably mounted in the housing 17, and a knob 18 is connected to the slide plate 19. As shown in FIG. 13, the slide 19 defines a first groove 19a opposite to a position of the lever 5(A) of the seesaw switch A, a second groove 19b opposite to a position of the lever 5(B) of the lever switch B and a third groove 19c opposite to the lever 5(C) of the lever switch C, each being provided with a small amount of play.
As shown in FIG. 15, when the knob 18 is manually actuated such that the slide plate 19 moves in the direction X1, a side of the groove 19a engages the lever 5(A), thereby causing the lever 5 to rotate in the seesaw switch A in the direction of the arrow .THETA. (clockwise) into a first operating position in which a seat is moved, for example, forward by a motor and a power transmission system (not shown). Similarly, when the knob is manually actuated in the direction of the arrow X2, the lever 5(A) engages with the first groove 19a and is turned in the counterclockwise direction, thereby causing, for example, the seat to move backward. If the knob 18 is released from either of the first or second operating positions, the lever 5 returns to a neutral position and the seat remains at a desired position. In addition, as shown in FIG. 14, when a first end of the knob 18 is moved to the left, a side of the groove 19c of the slide plate 19 causes the lever 5(C) to pivot counterclockwise into a third operating position in which, for example, a front of the seat ascends. Similarly, when the first end of the knob 18 is moved to the right, a side of the groove 19a causes the lever 5(C) to pivot clockwise into a fourth operating position in which, for example, the front of the seat descends. In a similar manner, the switch B is moved into fifth and sixth operating position in which, for example, a back of the seat is raised and lowered, by moving a second end of the knob to the right or to the left.
The above-described prior art switch of FIGS. 10-12 includes a single lever 5, each of which is actuated by manually pivoting a single knob 3. Consequently, if one end 3a of the knob 3 is pressed, then the other end 3b protrudes upward; therefore, the switch must be provided with an enough space to allow for the protruding end, thereby effecting the placement of other parts located next to the switch. This may bring about a big layout problem of the parts in situations in which the switch is used as a change-over switch for seat adjusting, for example, in automobiles where space is limited.
Further, when the switch is used in the switch apparatus of FIGS. 13-15 as a seat adjusting switch, since other switches arranged in a car are typically push-button types, the manipulation of the knob 18 is incompatible, thereby eliminating a sense of congruence. Still further, it is generally demanded that a push-button type switch apparatus operating on a large current be easily manufactured, as compared to the prior art switch apparatus.